The present invention relates to fluid flow control devices. Automatic fluid control devices are presently in common use, particularly in association with water faucets in sinks or toilets. More specifically, it is known in the art to utilize motion detectors and object detectors, such as infrared, electrostatic, temperature or radar sensors, to detect the presence of an object within a detection area necessitating the activation of a water flow device. Certain systems operate responsively to temperature-sensing devices, which activate the water valve based on temperature changes indicating the presence of the user proximate the sensor. In other systems, the valve activates responsively to infrared reflections indicating a user's presence.
Automatic faucets require a power source, for example to operate the components which detect the presence of a user and to open and close a valve to start or stop water flow. When such devices draw power from dedicated power sources, for example AC electric power lines found in commercial and residential buildings, power consumption is a relatively minor concern. However, it is often desirable to employ an energy storage element, for example one or more batteries, instead of relying on dedicated line power.
Unfortunately, energy storage elements have a finite operative life. To extend this life, and thereby reduce maintenance expense and inconvenience, some prior systems employ custom-made batteries, for example constructed from lithium. Although custom batteries may have a greater operative life than conventional batteries available to the public, they are, typically, expensive and constructed from hazardous materials requiring special disposal procedures.
In one known device, the control system deactivates when not in use, thereby preserving battery power. The system operates by sensing changes in an electrostatic field, which is monitored even when the system is in its deactivated state. Thus, the control system may be activated upon an appropriate disturbance in the electrostatic field to determine whether the valve should be activated. Unfortunately, the effectiveness of the electrostatic field may be reduced in certain circumstances where metal is present proximate the device.